Method of developing aged photosensitive material containing silver halide and a chromate



Patented Oct. 20, I953 STATES METHOD OF DEYELOPING .AGEDQHPHOTOLE- SENSITIVE; MATERIAL sCONTAINING... SILe- VER;HALIDIE AND A GHRDMATE Wilhelm N eugebauer and Maximilian: Karl Reichel; Wiesbadenl-Biebrich, Germany, assignors to Keuffel- &..Esserompany, Hoboken, N. J.

No Drawing; Application October 13, 1950, Serial'No. 190,041. In Germany October-24, 1949.1

8 Claims.

'materials used as intermediates in'the reproduction. of drawings. This type of photosensitive material serves as a duplicate tracing from which prints can be made in the usual manner. More particularly the. invention relates to photosensitive layers made up of a colloid (such as glue: or the like), an agent capable. of. hardening the colloid upon: exposureto light (such as chromate salts). and: a silver: halide.

When this. type of material is. exposed to light, thecol'loidlater is. hardened in the exposed areas and a latent silver halide image is also. formed. The: material is developed: byrubbing with waterto remove the colloid layer from the unexposed areas and itis then developed to. convert the. silver halide to a blacksilverimage in the exposed areas.

Thesenrnateri'als have the. disadvantage however that their shelf life or keeping quality is poor.- For this reason it is necessary to use these materials a short time after-the photosensitive colloid layer has been coated on the base sheet even if they were stored under conditions of lowtemperature and humidity... Materialwhich. was stored too long under unfavorable conditions. hadto. bediscarded because. it did not give satisfactory prints.

Now it. has. beenv found that satisfactory prints can be obtainedon. material .of this. typeeven .after months of storage. under conditions which formerly would have made the material. unusable, if the. exposed material is. subjected during the. development. of the. exposed materiaLto the. influence. of. certain mono -nitro-subs.tituted heterocyclic. compoundsconstituted. in such .a manner thatv a benzene .or naphthalene. nucleus is. condensed. together with .a fiveemembered closed heterocyclicchainselected from the. group consisting of c o N o. 0 C

m 3 U a m y a. 4

The position of the nitro group'is preferably in the benzene and naphthalenenucleus, respectively.

ATENT ()FFICE The. .heterocyclic. nitrocompound is caused to react with the lightrexposed material preferably in a weakly alkaline solution.

Compounds which may be used in accordance with this: invention are, for example, mono-nitrobenzimidazoles, mono nitro benzotriazoles, mono-nitro-benzopyrazoles; mono-nitro-benzothiazoles, mono-nitro-naphthoimidazoles, and mono-nitro-naphtho:triazoles. If for example 0.1 oi. fi-nitro-benzimidazole is added: to a sodaalkaline metol hydroquinone developing solution, the unexposed areas of the material developed therewith are free-of silver-fog, even if the photosensitive layer on the material is-so de'composed that itwou-ldnorma-lly have given an almost entirely black print.

Furthermore, it has been found that thesulfonation products of the mono-nitro-substituted heterocycliccompounds; of the naphthalene series which may be used in accordance with this invention-for the treatment of. light-exposed colloid layers containing silverhalide and a chromateg'yie-ld equally good-results. The sulfonation products arepreierably used as alkali metal salts.

It is importantthat the. -mono-nitro-substitutedheterocyclic compound be applied in the developing solution. Additionof the compound to :the photosensitive colloid layer is not efiective apparently because'oi, the chromates present therein.

However; Wherra developing solution containing, a'compound of thistype is. used on decomposed photosensitive zmaterial of the kind described a disturbing reddish discoloration of the background occurs. In order. to avoid this it is necessary to give the. developed material a quick treatment with-an acid fixing bath.

Images having high contrast. are-obtained from photo-sensitive material. containing a hardenable colloid such as glue, silver halide and chromate by development according to-this invention, even-ifsthe material has been storedfor months. or-under forced conditions, for example for '72 hours at 49 C. in air containing 98% relative humidity:

In order to illustrate the present invention the following 1 examples. are; inserted:

(1.) .A light-sensitive photosensitive intermediatevmaterial is .prepared bycoating tracing cloth waterproofed with a nitrocellulose lacquer with an aqueous colloidal dispersion containing the following ingredients:

5 liquid ounces of Le Pages photographic glue (fish glue),

9 liquid ounces of silver nitrate solution (3.07

ounces of C. P. salt in distilled water),

9 liquid ounces of potassium chloride solution (1.43 ounces of C. P. salt in distilled water),

77 liquid ounces of distilled water,

9 liquid ounces of ammonium bichromate (11 grams of C. P. salt in distilled water).

The material is stored for 72 hours under forced conditions (40 C. 90% relative humidity) and subsequently exposed to light under a suitable master. Thereafter the material is developed with an aqueous solution containing the following ingredients:

4 grams of metol,

12 grams of hydroquinone,

12 grams of sodium carbonate (water free),

44 grams of sodium sulfite (crystallized),

2.25 grams of G-nitro-benzimidazole (total volume=2250 com.)

A deep black silver image on a background free of fog is obtained. If the developer solution is used Without the adidtion of (i-nitro-benzimidrazole, a deep black silver layer covers the whole surface of the image making it impossible to distinguish any details of the negative image.

In order to avoid the formation of the disturbing reddish discoloration of the background, the above described copies of high cotrast are quickly treated with an acid fixing bath having the following composition:

50 grams of sodium sulfite (crystallized),

15 grams of tartaric acid,

200 grams of sodium thiosulfate (crystallized) in 1000 com. of distilled water, total volume.

Subsequently the copies are washed and dried.

The waterproofed tracing cloth base material may be replaced by a cellulose acetate foil saponified on its surface or even by metallic foils, for example, an aluminum foil or a zinc foil. Metallic foils, for example aluminum foils which have been covered with a surface layer consisting of metal oxide or metallic foils provided with a solid porous coating consisting of fluorine or phosphorous compounds provide a particularly good base material for the photosensitive layer and excellent prints can be made thereon.

(2.) The same colloidal layer as described in Example 1 containing fish glue, silver salt and dichromate is used for the preparation of the photosensitive layer on a suitable base, but in lieu of 2.25 grams of 6-nitro-benzimidazo1e 2.25 grams of fi-nitro-benzitriazole are added to the developer solution.

(3.) The same colloidal layer as described in Example 1 containing fish glue, silver salt and dichromate is used for the preparation of the photosensitive layer on a suitable base, but instead of 2.25 grams of G-nitro-benzimidazole 2.25 grams of S-nitro-benzopyrazole are added to the developer solution.

(4.) The same colloidal layer as described in Example 1 containing fish glue, silver salt and dichromate is used for the preparation of the photosensitive layer on a suitable base, but instead of 2.25 grams of G-nitro-benzimidazole 3.75 grams of sodium G-nitro-1,2-naphthoimidazole sulfonate are added to the developer solution.

(5.) The same colloidal layer as described in Example 1 containing fish glue, silver salt and dichromate is used for the preparation of the photosensitive layer on a suitable base, but in lieu of 2.25 grams of fi-nitro-benzimidazole a mixture consisting of 1.87 grams of sodium 6- nitro-naphthoimidazole sulfonate and 1.12 grams of 6-nitro-2-hydroxy-benzothiazole are added to the developer solution.

(6.) The same colloidal layer as described in Example 1 containing fish glue, silver salt and dichromate is used for the preparation of the photosensitive layer on a suitable base, but instead of 2.25 grams of G-nitro-benzimidazole 3.75 grams of sodium 6-nitro-1,2-naphthotriazole sulfonate are added to the developer solution.

After having fully described and explained our present invention, what we claim is:

l. The method of producing images rich in contrast from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a reducing agent for the exposed silver halide and a mono-nitro-substituted heterocyclic compound selected from the group of nitro substituted benzene and nitro substituted naphthalene condensed with a five-membered closed heterocyclic chain selected from the group consisting of C NC NC O C N 43 43 43 43 2. The method of producing images rich in contrast, from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a reducing agent for the exposed silver halide and a sulfonation product of a mononitro-substituted heterocyclic compound selected from the group of nitro substituted naphthalene condensed with a five-membered closed heterocyclic chain selected from the group consisting of o N o N o o c N 5 2 H 5 2 5 2! CUC, CVN, c 1 N and o 1 c N N N s 3. The method of producing images rich in contrast, from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a reducing agent for the exposed silver halide and G-nitro-benzimidazole.

4. The method of producing images rich in contrast, from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a reducing agent for the exposed silver halide and 6-nitro-benzotriazole.

5. The method of producing images rich in contrast, from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a reducing agent for the exposed silver halide and 6-nitro-benzopyrazole.

6. The method of producing images rich in contrast, from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a. reducing agent for the exposed silver halide and G-nitro-l.2-naphthoimidazole-sulfonic acid alkali salt.

7. The method of producing images rich in contrast, from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a reducing agent for the exposed silver halide and 6-nitro-1.2-naphthotriazole-sulfonic acid alkali salt.

8. The method of producing images rich in contrast from aged photosensitive material comprising a colloid layer containing silver halide and a chromate on a base, which comprises treating said material after its exposure to light under a master with a developing solution containing a reducing agent for the exposed silver halide and a mono-nitro-substituted heterocyclic compound selected from the group of nitro substituted benzene and nitro substituted naphthalene condensed with a five-membered closed heterocyclic chain selected from the group consisting of WILHELM NEUGEBAUER. MAXIMILIAN KARL REICHEL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,271,229 Peterson Jan. 27, 1942 2,384,593 Bean Sept. 11, 1945 Staufier Feb. 21, 1950 

1. THE METHOD OF PRODUCING IMAGES RICH IN CONTRAST FROM AGED PHOTOSENSITIVE MATERIAL COMPRISING A COLLOID LAYER CONTAINING SILVER HALIDE AND A CHROMATE ON A BASE, WHICH COMPRISES TREATING SAID MATERIAL AFTER ITS EXPOSURE TO LIGHT UNDER A MASTER WITH A DEVELOPING SOLUTION CONTAINING A REDUCING AGENT FOR THE EXPOSED SILVER HALIDE AND A MONO-NITRO-SUBSTITUTED HETEROCYCLIC COMPOUND SELECTED FROM THE GROUP OF NITRO SUBSTITUTED BENZENE AND NITRO SUBSTITUTED NAPHTHALENE CONDENSED WITH A FIVE-MEMBERED CLOSED HETEROCYCLIC CHAIN SELECTED FROM THE GROUP CONSISTING OF 